1. Technical Field
The invention relates generally to control equipment for controlling industrial or similar processes and particularly to self-tuning controllers. More particularly, the invention concerns feedforward controllers wherein operating parameters are developed in response to changes in the process inputs,
2. Background Art
Control systems regulate many material, energy and guidance systems. Feedforward control is a rarer and more specialized control method. Feedforward recognizes that upsets in the inputs to the system can be used to adjust the system devices in anticipation of or simultaneously with the arrival of those upsets. An advanced form of feedforward control is given in U.S. patent application Ser. No. 07/355,026, assigned to the assignee of the present invention, the teaching of which is incorporated herein by reference. If all the load variables for a particular process are sensed, transmitted, and responded to without error, and if the relationship between manipulated and measured variables is exactly known, then perfect control is theoretically possible provided the ideal feedforward controller is stable and physically realizable. Feedforward control is discussed at length in U.S. patent application Ser. No. 07/355,026, which describes an advanced adaptive control technique.
The present invention is directed to an adaptive feedforward control method and apparatus in which feedforward compensators tune for measured load variables. Because feedforward compensators are generally known to be difficult to tune manually and require retuning as process conditions change with the prior art apparatus, feedforward is not widely used. Feedforward controllers which reliably update their tuning constants after each naturally occurring isolated disturbance are unknown. As a result, many process control applications could advantageously incorporate adaptive feedforward control were such apparatus available.